Organisms have evolved a variety of systems and pathways to maintain the integrity of their genetic material. In recent years there has been an explosion of enzymatic and molecular biological data describing these pathways and highlighting their importance in protecting organisms from the deleterious effects of environmental damaging agents. Damage to DNA has been shown to result in a number of harmful effects including mutation, oncogenesis, cellular cytotoxicity and perhaps even aging. Defects in DNA repair have also been implicated in several human genetic diseases such as xeroderma pigmentosum, ataxia telangiectasia, Bloom's syndrome, Cockayne syndrome, Fanconi anemia, among others. Some of the genes involved in these disorders, as well as a number of other repair genes, have been cloned and plans for gene therapy are on the drawing board. In fact, DNA repair systems appear to be one of the most highly conserved in nature; homologies exist among DNA repair proteins from bacteria to humans. The subject of this symposium is the structure/function relationships between the proteins that interact with damaged DNA and the DNA damages. The purpose of this New York Academy of Sciences' sponsored meeting is to bring together structural biologists, chemists, and DNA repair enzymologists, to focus on the structural alterations produced in DNA by damage and how these alterations influence recognition by biologically relevant proteins such as DNA and RNA polymerases and repair glycosylases and endonucleases. The disciplines are well represented by the speakers who include a number of young investigators. Poster sessions will be an integral part of this meeting and will provide an additional venue for young investigators to present their work.